Currently, a dual-frequency antenna is required to receive the data present in the L1 (1.575 GHz) and L2 (1.227 GHz) signals transmitted by the satellites in the Global Positioning System (GPS). There are several different types of dual-frequency patch antennas that are capable of receiving (or transmitting) two signals, such as the L1 and L2 signals used in the GPS. Among these dual-frequency patch antennas are (a) orthogonal-mode dual-frequency antennas with a single-point or dual-point feed, (b) multi-patch dual-frequency antennas in which the patches are stacked or co-planar, and (c) reactively loaded patch antennas in which the reactive loading is achieved using a stub, notch, pin, capacitor, or slot. A discussion of each of these types of dual frequency antennas can be found in Maci et al., Dual-Frequency Patch Antennas, IEEE Antennas and Propagation Magazine, December 1997, pp. 13-20, Vol. 39, No. 6, which is incorporated herein by reference. Generally, a stacked patch antenna comprises: (a) ground plane, (b) a first patch (i.e., a thin metallic region) disposed to one side of the ground plane, (c) a second patch disposed between the ground plane and the first patch, (d) a dielectric structure disposed between the first and second patches and between the second patch and the ground plane, and (e) a feed structure for conveying an electrical signal having a first frequency to and/or from the first patch and an electrical signal having a second frequency to and/or from the second patch.